1. Field of the Invention
The present invention relates to a disk brake that suitably applies braking force to a vehicle such as an automobile.
2. Description of the Related Art
In general, a disk brake provided at a vehicle such as an automobile comprises: a mounting member mounted on a non-rotating portion of the vehicle where the mounting member includes a pair of arms that is separated along a rotating direction of a disk and extends over the exterior of the disk in its axial direction; a caliper slidably provided at each of the arms of the mounting member; a pair of friction pads slidably supported by each of the arms of the mounting portion through a pad spring where the pair of friction pads are pressed toward the disk by means of the caliper; and the like.
In the conventional disk brake categorized by this type, when a driver performs braking operation, a piston provided on the inner side of the caliper is adapted to slidably shift toward a side of the disk by hydraulic pressure externally supplied, whereby the friction pads provided on the inner side of the caliper are pressed toward the disk. The caliper is then slidably shifted relative to the mounting member by means of counterforce generated, so that each of the friction pads is pressed to each side of the disk between its outer leg portion and the piston so as to apply braking force to the disk rotated.
In this case, at each of the arms of the mounting portion, a pad guide in which to slidably guide the pair of friction pads in the axial direction of the disk is provided. Further, at each of the arms of the mounting portion, the pad spring in which to elastically support the pair of friction pads with each of the arms is provided. This pad spring can inhibit that the friction pads are shook relative to the pad guide of the arms, etc. whereby the friction pads can slide smoothly.
Furthermore, the friction pads extend either in the rotating direction or in the circumferential direction of the disk and comprise: a back plate where ear portions (or engagement portions) in a convex formation are provided at each end side of the back plate, the ear portions slidably engaging with the pad guide of the mounting member; and a lining made of friction materials that is provided on the surface of the back plate.
Still further, the disk brake provided with a return spring is known. The return spring works as that, when braking to the vehicle is released, the return spring urges each of the friction pads in a direction separating from each side of the disk. The return spring is provided between the mounting member and the friction pads and urges the friction pads in a return direction, that is, separating the friction pads from the disk. See, for example, Japanese Patent Application Laid-open No. 2002-327780 (to be referred to as Patent Document 1).
Moreover, the base end side of the return spring is fixed at a position corresponding to the ear portions of the back plate of the friction pads. The top end side of the return spring, on the other hand, is elastically abutted to the mounting member through the pad spring whereby the friction pads are normally urged toward a return position, that is, a position axially outside of the disk.
Here, in the conventional art as discussed above, the base end side of the return spring is fixed at the bottom side of the convex ear portions of the back plate of the friction pads while the top end side of the return spring is arranged as extending over the pad guide of the mounting member in the circumferential direction of the disk and abutting (or elastically abutting) to the side of the arms of the mounting member through the pad spring.
However, since the return spring in the conventional art is structured as that the return spring in its thickness direction is oriented toward the circumferential direction of the disk, for example, in case that the caliper is a twin-bore, and/or in case that a friction detecting portion is provided at the return spring, etc., a mounting space for layout becomes small whereby it may cause difficulties to arrange the return spring between the mounting member and the friction pads.
Still further, in case of the conventional return spring, when the friction pads are urged in the return direction separating the friction pads from the disk by releasing braking of the vehicle, there may be a case that the friction pads are inclined relative to the surface of the disk. As a result, uneven wear may occur on the friction pads, or run-out of the friction pads or brake noise may occur.